Methods and devices for providing prolonged drug therapy

ABSTRACT

Methods and devices for maintaining a desired therapeutic drug effect over a prolonged therapy period are provided. In particular, oral dosage forms that release drug within the gastrointestinal tract at an ascending release rate over an extended time period are provided. The dosage forms may additionally comprise an immediate-release dose of drug.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.09/070,666, filed Apr. 30, 1998, which is a continuation of U.S.application Ser. No. 08/910,593, filed Jul. 31, 1997, which claims thebenefit of U.S. Provisional Application Nos. 60/030,514 and 60/044,121,filed Nov. 12, 1996 and Apr. 22, 1997, respectively.

This application is also a continuation-in-part of U.S. application Ser.No. 08/967,606, filed Nov. 10, 1997, which claims the benefit of U.S.Provisional Application No. 60/031,741, filed Nov. 25, 1996.

This application is also a continuation-in-part of U.S. application Ser.No. 08/937,336, filed Aug. 19, 1997.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention pertains to methods and devices for maintaining a desiredtherapeutic drug effect over a prolonged therapy period. In particular,the invention is directed to methods and devices that provide drugrelease within the gastrointestinal tract at an ascending release rateover an extended time period. In this manner, drug is released at anascending rate during a portion of the drug administration periodsufficient to maintain a desired therapeutic drug effect throughout aprolonged therapy period.

2. Description of the Related Art Including Information Disclosed Under37 CFR 1.97 and 1.98

To produce its pharmacological effects, a drug must be made available inappropriate concentrations at its site of action within the body. Thisavailability is affected by numerous factors including the quantity ofthe drug administered, the extent and rate of its absorption from itsadministration site, its distribution, binding or localization withintissues, its biotransformation and its excretion. One commonly-usedindicator of drug availability is the concentration of drug that isobtained within the blood or plasma, or other appropriate body fluid ortissue, of a patient following administration of the drug. Forconvenience, this concentration may be referred to as “plasma drugconcentration” hereinafter which is intended to be inclusive of drugconcentration measured in any appropriate body fluid or tissue. Plasmadrug concentration measurements provide very useful informationincluding, for example, comparative information with regard to differentdrug dosage forms and/or different drug administration routes. Inaddition, for many drugs, various drug effects including both desiredpharmacological effects, i.e., therapeutic drug effects, and undesiredpharmacological effects, i.e., side effects, have been correlated withspecific plasma drug concentrations or ranges of plasma drugconcentrations.

For orally administered drug dosage forms, absorption occurs within thegastrointestinal (“g.i.”) tract and is affected by many factorsincluding the physicochemical properties of the local microenvironment,such as surface area, blood flow and membrane characteristics (whichvary significantly in the different portions of the g.i. tract), thephysicochemical properties of the drug entity, drug concentration, theexistence and activity of drug-specific transport mechanisms, etc. Oneimportant factor in the rate of absorption of drug administered as anoral dosage form is the rate at which drug is released from the dosageform. Drug release rates for oral dosage forms are typically measured asan in vitro rate of dissolution, i.e., a quantity of drug released fromthe dosage form per unit time.

Conventional oral dosage forms can be described as “immediate-release”because, generally, essentially the entire dose of drug is released fromthe dosage form within a very short period, i.e., minutes, followingadministration. As this bolus of released drug is absorbed, the plasmadrug concentration typically rapidly rises to a maximal or peakconcentration and subsequently declines as the drug is distributed,bound or localized within tissues, biotransformed and/or excreted. Thetime period for this decline varies for different drugs and depends onmany factors but this time period will be characteristic of a particulardrug. Generally, during some portion of the time period in which theplasma drug concentration rises, peaks and declines, the drug providesits therapeutic effects, i.e., the plasma drug concentration achieves orexceeds an effective concentration. Moreover, at some point during thistime period, the therapeutic effects disappear, i.e., when the plasmadrug concentration declines to a level that is below an effectiveconcentration. In addition, often, during a portion of this timesurrounding the time the peak concentration is attained, i.e., when theplasma drug concentration is in its highest range, undesired sideeffects may become apparent.

In view of the above, it will be appreciated that continued drugeffectiveness occurs during the time period when the plasma drugconcentration is within the effective plasma drug concentration range.Because the plasma drug concentration declines over time, however,multiple is doses of the immediate-release drug dosage form must beadministered at appropriate intervals to ensure that the plasma drugconcentration remains in or, again, rises to, the effectiveconcentration range. At the same time, however, there is a need to avoidor minimize plasma drug concentrations that rise to, and/or that remainfor too long within, the higher ranges where side effects becomeapparent. Accordingly, for many drugs, multiple, separate doses of theimmediate-release dosage form must be administered at appropriateintervals to maintain a satisfactory balance of desired and undesiredpharmacological effects over a prolonged therapy period.

One focus of efforts to improve drug therapy has been directed toproviding non-immediate-release oral drug dosage forms that affectabsorption of the drug primarily by altering the release rate of thedrug from the dosage form. Examples of such non-immediate-releasedelivery systems include delayed-release and sustained-release systems.Sustained-release dosage forms generally release drug for an extendedtime period compared to an immediate-release dosage form. There are manyapproaches to achieving sustained release of drugs from oral dosageforms known in the art. These different approaches include, for example,diffusion systems such as reservoir devices and matrix devices,dissolution systems such as encapsulated dissolution systems (including,for example, “tiny time pills” ) and matrix dissolution systems,combination diffusion/dissolution systems, osmotic systems andion-exchange resin systems as described in Remington's PharmaceuticalSciences, 1990 ed., pp. 1682-1685.

It is believed to be particularly desirable to provide sustained-releaseoral dosage forms that provide drug release at a substantially constantrelease rate over an extended time period. In this manner, for manydrugs, the plasma drug concentration initially ascends for a shortperiod of time as drug release begins and then remains substantiallyconstant over an extended time period as drug release continues at aconstant rate. For many drugs, this substantially constant plasma drugconcentration correlates with substantially constant drug effectivenessover a prolonged therapy period. In addition, because an initialrelatively high peak plasma drug concentration is avoided, side effectsmay be less of a problem. Accordingly, advantages of constant-releasedosage forms include decreasing the number of doses of a drug that needto be administered over time and providing a better balance of desiredand undesired pharmacological effects of the drug.

Osmotic dosage forms, in particular, have been notably successful atproviding constant-release of drugs over extended time periods. Osmoticdosage forms, in general, utilize osmotic pressure to generate a drivingforce for imbibing fluid into a compartment formed, at least in part, bya semipermeable wall that permits free diffusion of fluid but not drugor osmotic agent(s), if present. A substantially constant rate of drugrelease can be achieved by designing the system to provide a relativelyconstant osmotic pressure and having suitable exit means for the drugformulation to permit the drug formulation to be released at a rate thatcorresponds to the rate of fluid imbibed as a result of the relativelyconstant osmotic pressure. A significant advantage to osmotic systems isthat operation is pH-independent and thus continues at theosmotically-determined rate throughout an extended time period even asthe dosage form transits the gastrointestinal tract and encountersdiffering microenvironments having significantly different pH values.

Surprisingly simple but highly effective osmotic devices comprising drugin a mixture with excipients, optionally including osmotically activecomponent(s), within the compartment are known in the art. Althougheffective for many drugs, the release rate in these devices oftendeclines over time and complete delivery of the drug load may not occur.A more sophisticated type of osmotic device comprises two componentlayers within the compartment formed by the semipermeable wall. Onecomponent layer comprises drug in a mixture with excipients, optionallyincluding osmotically active component(s), that will form a deliverabledrug formulation within the compartment and the second component layercomprises osmotically active component(s) but does not contain drug. Theosmotically active component(s) in the second component layer typicallycomprise osmopolymer(s) having relatively large molecular weights andwhich exhibit “swelling” as fluid is imbibed such that release of thesecomponents through the drug formulation exit means does not occur. Thesecond component layer is referred to as a “push” layer since, as fluidis imbibed, the osmopolymer(s) swell and push against the deliverabledrug formulation of the first component layer to thereby facilitaterelease of the drug formulation at a substantially constant rate. Theabove-described devices are known, for example, from the following USPatents, owned by Alza Corporation: U.S. Pat. Nos. 4,327,725; 4,612,008;4,783,337; and 5,082,668, each of which is incorporated in its entiretyby reference herein.

Although constant-release dosage forms have proven effective for manydifferent drug therapies, there are clinical situations where these havenot been entirely satisfactory. It has been observed that for somepatients being treated with constant-release dosage forms for someconditions or diseases, the therapeutic effectiveness of the drugdecreases at time periods before the end of the desired therapy perioddespite the maintenance of substantially constant drug release thatwould be expected to provide continued effectiveness. Accordingly, thereremains a need to provide methods and devices for maintaining a desiredtherapeutic drug effect over a desired prolonged therapy period whensustained-release dosage forms that release drug at a substantiallyconstant rate over an extended time period are not satisfactory.

BRIEF SUMMARY OF THE INVENTION

One aspect of the present invention pertains to providing improved drugtherapy for those clinical situations where therapeutic effectiveness ofan administered drug therapy unexpectedly decreases at time periodsbefore the end of the intended therapy period. It has been surprisinglydiscovered that, in an exemplary clinical situation, administration ofdrug at a release rate that is ascending, rather than substantiallyconstant, over an extended time period provided therapeutic efficacythat did not decrease before the end of the prolonged therapy period.

With the discovery that administration of drug at a release rate that issubstantially ascending provides improved drug therapy, a need arisesfor sustained-release oral dosage forms adapted to provide such arelease rate over a suitable extended time period. Accordingly, otheraspects of the present invention include providing oralsustained-release dosage forms that provide an ascending drug releaserate over an extended time period, methods of making such dosage formsand methods of using such dosage forms to maintain therapeuticeffectiveness for a desired prolonged therapy period.

It has been surprisingly discovered that oral osmotic dosage formsexhibiting an ascending drug release rate for an extended time periodcan be achieved. In particular, the present invention is directed toosmotic dosage forms having bi-layer or tri-layer tablet cores that areadapted to provide ascending drug release rates over an extended period.In addition, to provide for an initial rapid onset of drug action, thepresent invention is also related to dosage forms that additionallycomprise a dose of drug for immediate release.

The bi-layer oral osmotic dosage forms of the present invention includea first component layer, comprising a selected drug and excipients forforming a deliverable drug composition when hydrated, and a second pushlayer, comprising a fluid-expandable osmopolymer and excipients,contained within a compartment formed by a semipermeable membrane andhaving exit means for drug release from the compartment. The two layersare compressed into bi-layer tablet cores before the semipermeablemembrane is applied and a suitable orifice for drug release therethroughis formed. Importantly, the bi-layer tablet cores disclosed herein areformed when two component layers are compressed together to provide alongitudinally compressed tablet (“LCT”) core having a “capsule-shaped”configuration with a different layer at each narrow end.

The combination of features including the osmotic properties of thecomponent layers, the fluid flux properties of the semipermeablemembrane and the configuration of the tablet core ensures that drug isreleased at an ascending rate over an extended time period. In apreferred embodiment, sufficient activity in the push layer is achievedby use of a relatively large concentration (at least about 35%) ofosmotically effective solute, or osmagent, such as sodium chloride. Inaddition, sorbitol is preferably included in the first component layer.

The tri-layer oral osmotic dosage forms of the present invention includea novel tri-layer tablet core surrounded by a semipermeable membrane andhaving suitable exit means for releasing drug formulation through thesemipermeable membrane. The novel tri-layer tablet core has a firstdrug-containing layer, a second drug-containing layer and a third pushlayer. In operation, through the cooperation of the dosage formcomponents, drug is successively released from the first drug-containinglayer and then from the second drug-containing layer. It has beendiscovered that a drug concentration gradient facilitates theachievement of an ascending drug release rate for an extended timeperiod. Consequently, the other excipients in the drug-containing layersmay be more flexibly varied and adjusted for other purposes such asmanufacturing convenience and pharmaceutical elegance. In this manner,dosage forms that exhibit reliable drug release having the desiredsustained and ascending rate over an extended time period can bereliably and efficiently manufactured.

It is preferred to use the LCT core configuration, as described above,to enhance hydration of the tri-layer core. In addition, aflux-enhancing agent is preferably included in the semipermeable wallcomposition. In a presently preferred embodiment, the combination offeatures including the LCT tri-layer core configuration, a suitable drugconcentration gradient between the first and second component layers,the osmotic properties of the component layers and the fluid fluxproperties of the semipermeable membrane achieves the desired ascendingrate of drug release over an extended time period.

There are numerous clinical situations and drug therapies that could beimproved with the use of dosage forms that provide a sustained andascending release rate over an extended time period. Exemplary dosageforms, as disclosed herein, comprise CNS-acting drugs andcardiovascular-acting drugs. It will be appreciated by persons of skillin the art that the invention is applicable to many other types of drugsand drug therapies. Examples of suitable types of drugs include, but arenot limited to, anti-infectives, analgesics, anesthetics,antiarthritics, antiasthmatics, anticonvulsants, antidepressants,antidiabetics, antidiarrheals, antihistamines, antiinflammatories,antimigraines, antineoplastics, antiparkinsonisms, antipruritics,antipsychotics, antipyretics, antispasmodics, anticholinergics,sympathomimetics, calcium channel blockers, beta blockers,antiarrythmics, antihypertensives, ACE inhibitors, diuretics,vasodilators, decongestants, hormones, hypnotics, immunosuppresives,parasympathomimetics, prostaglandins, proteins, peptides, sedatives andtranquilizers.

The exemplary clinical situation described herein involves treatment ofADHD with methylphenidate therapy. Accordingly, the present inventionalso pertains to making oral methylphenidate sustained release dosageforms that provide a sustained and ascending release rate of a drug overan extended time period.

It has further been discovered that oral methylphenidate sustainedrelease dosage forms that provide an ascending release rate of a drugover an extended time period can be used to provide effective once-a-daytherapy for ADHD. Thus, the present invention also pertains to improvingdrug therapy for ADHD by eliminating the need for multiple daily dosesof methylphenidate yet providing therapeutic efficacy throughout the daythat compares to the therapeutic efficacy provided by multiple doses ofimmediate release methylphenidate.

The above-described features and advantages, as well as others, willbecome more apparent from the following detailed disclosure of theinvention and the accompanying claims.

Although the present invention is illustrated herein by exemplary dosageforms containing specific exemplary drugs, methods of making such dosageforms and methods of using methylphenidate-containing dosage forms toprovide a desired therapeutic outcome, the invention is not limited bythe exemplary embodiments. The invention broadly embraces oralsustained-release dosage forms that provide an ascending drug releaserate over an extended time period, methods of making such dosage formsand methods of using such dosage forms to maintain therapeuticeffectiveness for a desired prolonged therapy period with respect to anyappropriate drugs and drug therapies as would be apparent to a person ofskill in the art in view of the disclosure herein.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a cross-section view of a bi-layer osmotic dosage form inaccord with the present invention.

FIG. 2 is a cross-section view of a tri-layer osmotic dosage form,additionally comprising an immediate-release drug overcoat and anaesthetic overcoat, in accord with the present invention.

FIG. 3 is a graph illustrating the quantity of drug released over timefrom a preferred embodiment of the present invention as described inExample 6.

FIG. 4 is a graph illustrating the plasma drug concentration over timeobtained following administration of methylphenidate in accord with anexperimental regimen (open diamonds) and a standard regimen (closedcircles) as described in Example 7.

DETAILED DESCRIPTION OF THE INVENTION

Many effective drug therapies utilize immediate-release oral dosageforms administered at spaced intervals to provide and maintain a desiredtherapeutic effect over a prolonged therapy period. In addition,sustained-release dosage forms for many drugs are known and, inparticular, constant-release oral dosage forms are known. There are manyexamples of effective drug therapies that utilize constant-release oraldosage forms to provide a desired therapeutic effect over a prolongedtherapy period. In many cases, these drug therapies offer advantagesover drug therapies that utilize immediate-release oral dosage formsadministered at spaced intervals. There are clinical situations,however, where the constant-release dosage form has unexpectedlyexhibited decreases in therapeutic effectiveness at time periods beforethe end of the desired prolonged therapy period.

One example of a clinical situation where drug therapy withsustained-release oral drug dosage forms that provide a substantiallyconstant rate of drug release for an extended period has not beenentirely satisfactory is with the use of central nervous system (CNS)stimulant drugs to treat various conditions and disorders includingAttention Deficit Disorder (ADD) and Attention Deficit HyperactivityDisorder (ADHD). These disorders are commonly diagnosed in children butcan also occur in adults. Treatment of these and other psychologicalconditions with CNS stimulant drugs has a long history. About 25 yearsago, methylphenidate replaced amphetamine as the primary stimulantprescribed to treat ADHD in children.

Methylphenidate therapy in children with ADHD has been extensivelystudied and the efficacy and safety of this treatment iswell-established. Methylphenidate therapy has been shown to be veryeffective in reducing symptoms of hyperactivity, inattention andimpulsivity in children with ADHD. The goal of drug therapy is tocontrol the behavioral symptoms during the daytime while the patient isin school or otherwise involved in activities where symptom controlbenefits the patient's ability to learn and/or otherwise beneficiallyparticipate in activities. Because of concerns related to side effects,however, drug therapy is typically discontinued during at least aportion of the evening and through the night in most patients. Dependingon the patient's particular circumstances, drug therapy may or may notbe discontinued over the weekends as well.

Treatment commonly utilizes immediate-release methylphenidateadministered two or three times during the day. For various is reasons,patients often experience difficulty complying with this administrationschedule. Because of abuse potential, methylphenidate is a controlledsubstance and thus drug access is a special concern. This dosage regimengenerally requires that at least one dose is administered during theschool day and, as a rule, children are not permitted to self-administerthe drug at school. For this reason, authorized school personnelgenerally take on the responsibility for administering the drug tochildren during the school day, however, this approach raises issues ofmedical privacy and potential stigmatizing of the child by peers. Inaddition, the compliance issue becomes further complicated astransportation, storage and supply of the drug typically must bedocumented and/or monitored and the schedules of the different partiesinvolved, i.e., the child, the educators and the authorized schoolpersonnel, must be coordinated and accommodated. The unfortunate resultis that doses may be given late or missed altogether resulting indecreased efficacy of the therapy.

For all of the above reasons, it would appear that a sustained-releaseoral dosage form of methylphenidate that provided substantially constantdrug release over an extended period to thereby eliminate the need fordose administration during the school day would be a welcomeimprovement. In fact, such a sustained-release dosage form ofmethylphenidate has been commercially available for several years.Clinical experience with this dosage form, however, has beendisappointing in that behavioral symptoms in patients taking thecontrolled-release dosage form is less well-controlled later in the daycompared to those patients taking multiple doses of theimmediate-release dosage form. In addition, the slower onset of actionof the controlled-release dosage form compared to the immediate-releasedosage form is unsatisfactory for many patients.

It has been surprisingly discovered that administration ofmethylphenidate at a release rate that is substantially ascending,rather than substantially constant, over an extended time periodprovided therapeutic efficacy similar to the efficacy obtained withmultiple doses of immediate-release methylphenidate dosage forms.Details of this discovery are disclosed in copending U.S. applicationSer. No. 910,593, filed Jul. 31, 1997, of which the present applicatianis a continuation-in-part application. To briefly review, in oneclinical study, a comparison of the behavioral, attentional, andcognitive efficacy of placebo and methylphenidate administered accordingto three different release rate regimens, i.e., immediate-release,constant-release and ascending-release, was performed. Theimmediate-release methylphenidate was administered as two spaced-apartdoses. The constant-release regimen was administered as an initialloading dose with the remaining total quantity administered in equalsmall doses at closely-spaced intervals extending past the time ofadministration of the second immediate-release dose. Theascending-release regimen was administered as an initial loading dosewith the remaining total quantity administered in increasing small dosesat closely-spaced intervals extending past the time of administration ofthe second immediate-release dose.

In this study, the constant-release regimen was observed to havedecreased clinical effectiveness compared to the immediate-releaseregimen at evaluation periods following administration of the secondimmediate-release dose. On the other hand, the ascending-release regimendemonstrated comparable clinical efficacy to the immediate-releaseregimen during these evaluation periods. Thus, the ascending-releaseregimen avoided the decrease in therapeutic efficacy seen with theconstant-release regimen at later time periods during the prolongedtherapy period.

While not making any assertions with respect to mechanism(s) of actionof the present invention, it is noted that the development of acutetolerance to methylphenidate has been proposed as an explanation for theunsatisfactory decrease in therapeutic effectiveness that has beenobserved in some cases. Support for this theory was demonstrated in asecond clinical study wherein a decrease in effectiveness ofmethylphenidate was seen over a prolonged therapy period both when aconstant-release regimen was utilized as well as when veryclosely-spaced doses of immediate-release methylphenidate dosage formswere administered. An ascending-release regimen, however, was shown tomaintain therapeutic efficacy throughout the prolonged therapy period.

With the discovery that drug effectiveness over a prolonged therapyperiod may be improved in some circumstances with administration of drugin an ascending release rate over an extended period, a need arises forsustained-release oral dosage forms adapted to provide such a releaserate. In one aspect of the present invention, it has been surprisinglydiscovered that bi-layer oral osmotic dosage forms can be adapted tomeet this need. In another aspect, it has been surprisingly discoveredthat sustained-release oral osmotic dosage forms having novel tri-layercores can be produced that also achieve sustained release of drugformulations at an ascending rate for an extended time period.

As is known in the prior art, osmotic dosage forms comprising compressedtablet cores require a short time period following administration inwhich to become hydrated sufficiently to begin releasing drug. For somedrug therapies, the slight delay in initial drug release isunsatisfactory. This problem is overcome with the addition of an initialdose of drug supplied in an immediate-release overcoat applied to thesurface of the semipermeable membrane. In preferred embodiments of thepresent invention, as disclosed herein, such an immediate-release drugovercoat is applied onto the surface of the bi-layer or tri-layerosmotic dosage forms.

For purposes of this disclosure, the following definitions shall apply:

For clarity and convenience herein, the convention is utilized ofdesignating the time of drug administration as zero hours (t=0 hours)and times following administration in appropriate time units, e.g., t=30minutes or t=2 hours, etc.

As used herein, the term “drug” generally refers to a pharmacologicallyactive substance that, when delivered into a living organism, produces adesired, usually beneficial, effect. Drug compositions are generallyutilized clinically in the form of a pharmaceutically acceptable saltthereof. In addition, some drug compositions exhibit chirality and,thus, have more than one optical isomer. Because the different opticalisomers may exhibit different pharmacological effects, it may beadvantageous to utilize a substantially pure form of one optical isomerof a drug, or a pharmaceutically acceptable salt thereof. Accordingly,the term “drug” refers to a clinically useful form of a drug compositionincluding a pharmaceutically acceptable salt thereof and including asubstantially pure isomer of the drug composition and a pharmaceuticallyacceptable salt thereof. Although a limited number of drugs arerepresented in the exemplary embodiments herein, the invention is not tobe limited by the exemplary embodiments but is fully applicable to othersuitable drugs as would be understood by persons of skill in the art.

The amount of drug incorporated in the dosage forms of the presentinvention varies depending on the particular drug, the therapeuticindication and the desired administration period, e.g., every 12 hours,every 24 hours, etc. Depending on the dose of drug desired to beadministered, one or more of the dosage forms may be administered.

A drug “release rate” refers to the quantity of drug released from adosage form per unit time, e.g., milligrams of drug released per hour(mg/hr). Drug release rates are calculated under in vitro dosage formdissolution testing conditions known in the art. As used herein, a drugrelease rate obtained at a specified time “following administration”refers to the in vitro drug release rate obtained at the specified timefollowing implementation of an appropriate dissolution test. Thedissolution test utilized in the Examples described herein wereperformed on dosage forms placed in metal coil sample holders attachedto a USP Type VII bath indexer and immersed in about 50 ml of acidifiedwater (pH=3) equilibrated in a constant temperature water bath at 37° C.Aliquots of the release rate solutions were injected into achromatographic system to quantify the amounts of drug released duringthe testing intervals.

A commonly-used reference measurement for evaluating drug release fromoral dosage forms is the time at which 90% of drug within a dosage formhas been released. This measurement is referred to as the “T₉₀” for thedosage form.

An “immediate-release” dose of a drug refers to a dose that issubstantially completely released within a time period of about 1 houror less and, preferably, about 30 minutes or less. An immediate-releasedose of drug applied as a coating on the surface of a dosage form, asused herein, refers to a dose of a drug prepared in a suitablepharmaceutically acceptable carrier to form a coating solution that willdissolve rapidly upon administration to thereby provide animmediate-release dose of drug. As is known in the art, suchimmediate-release drug overcoats may contain the same or a differentdrug or drugs as is contained within the underlying dosage form.

A “periodic release rate” refers to the quantity of drug released from adosage form during a specified periodic interval as determined at theend of that specified periodic interval, i.e., at each periodic intervalwhen a determination-is made, the quantity of drug released representsthe periodic release rate during that periodic interval. For example,the quantity of drug released as determined at t=1 h represents theperiodic release rate from the dosage form during the first hourfollowing administration and the quantity of drug released as determinedat t=2 h represents the periodic release rate during the second hourfollowing administration, etc.

An “ascending release rate” refers to a periodic release rate that isincreased over the immediately-preceding periodic release rate, wherethe periodic intervals are the same. For example, when the quantity ofdrug released from a dosage form is measured at hourly intervals and thequantity of drug released during the fifth hour following administration(determined at t=5 hours) is greater than the quantity of drug releasedfrom the dosage form during the fourth hour following administration(determined at t=4 hours), an ascending release rate from the fourthhour to the fifth hour has occurred.

It will be appreciated that the first periodic release rate measured,e.g., the periodic release rate at t=1 hour (unless equal to 0), willalways be greater than the release rate during the preceding period,e.g., the hour before the dosage form was administered, and, thus, thefirst periodic release rate always constitutes an occurrence of anascending release rate.

The ascending release rates described herein refer to the release ratefrom a dosage form adapted to provide sustained release of drug and donot include release of drug from any immediate-release drug coating thatmay be applied to the dosage form. In dosage form embodimentsadditionally comprising an immediate-release dose of a drug applied as acoating onto the underlying dosage form, the drug release measured att=1 hour will generally reflect both the drug released from theimmediate-release drug coating and any drug released from the underlyingdosage form, however, the quantity of drug released from the drugovercoat is disregarded in determining whether the drug release rate att=2 hours is greater than the drug release at t=1 hour.

As used herein with reference to the time period during which anascending release rate is provided, “an extended time period” refers toa time period beginning at t=0 hours and continuing through at least themid-point, and preferably beyond the mid-point, of the relevant T₉₀ ofthe dosage form. Because the dosage forms of the present invention areintended to provide sustained release of drug, a suitable T₉₀ forpurposes of this invention is at least about 6 hours and, consequently,the “extended time period” during which an ascending release rate isprovided is at least 3 hours.

In accord with the above-recited definitions, an “ascending release rateover an extended time period” refers to ascending release rates of drugobtained from the time of administration of the dosage form through, andpreferably beyond, the mid-point of the relevant T₉₀ for the dosageform. To illustrate, consider a situation where a dosage form has a T₉₀of about 8 hours. In this situation, an “ascending release rate over anextended time period” is achieved when the release rate at each hourthrough t=4 hours is greater than the release rate in theimmediately-preceding hour. Preferably, the release rate continues toascend during time periods beyond t=4 hours.

Bi-layer oral osmotic dosage forms and methods of making and using suchdosage forms are known in the art, for example, as described and claimedin the following US Patents, owned by Alza Corporation: U.S. Pat. Nos.4,327,725; 4,612,008; 4,783,337; and 5,082,668, each of which isincorporated in its entirety by reference herein. The prior art bi-layerosmotic dosage forms achieve sustained release of drug formulationswherein a relatively brief initial period of ascending release rates isfollowed by substantially constant release rates over a major portion ofthe T₉₀ period. The achievement of an ascending release rate for anextended time period of at least 50% of the T₉₀ period is not foundwithin the prior art. The dosage forms of the present invention areuseful for providing continuous effective drug therapy over a prolongedtherapy period without exhibiting a decrease in effectiveness during thelatter portion of the prolonged therapy period.

The bi-layer oral osmotic dosage forms of the present invention includea first component layer, comprising a selected drug and excipients forforming a deliverable drug composition when hydrated, and a second pushlayer, comprising a fluid-expandable osmopolymer and excipients, whereinthe two layers are compressed into bi-layer tablet cores before thesemipermeable membrane is applied and a suitable orifice for drugrelease therethrough is formed. The combination of features includingthe osmotic properties of the component layers, the fluid fluxproperties of the semipermeable membrane and the configuration of thetablet core ensures that drug is released at an ascending rate over anextended time period.

Importantly, the bi-layer tablet cores of the present invention areconfigured such that each component layer is substantially round incross-dimension with a circumferential width and a length between a topand a bottom end. The two layers are compressed together longitudinallysuch that the resulting bi-layer tablet core has the samecircumferential width as the component layers and a length that combinesthe lengths of the component layers. The overall configuration can bedescribed as “capsule-shaped” wherein the bi-layer tablet core has acircumferential width that is less than its length and has a rounded“narrow” top end and a rounded “narrow” bottom end and wherein eachnarrow end comprises a different component tablet layer.

For purposes of this disclosure, the above-described tablet cores arereferred to as longitudinally compressed tablet (“LCT”) cores. This LCTconfiguration ensures that, as the push layer expands longitudinallywithin the compartment formed by the semipermeable membrane, the surfacearea of the push layer in contact with the semipermeable membrane isincreased more than when other configurations are used.

In a preferred embodiment, sufficient activity in the push layer isachieved by use of a relatively large concentration (at least about 35%)of osmotically effective solute, or osmagent, such as sodium chloride.Consequently, the size of the push layer is relatively large and may beslightly larger than the first component layer containing the drug andexcipients. In addition, for certain embodiments, sorbitol was found tobe a useful excipient in the first component layer. It has beensurprisingly discovered that the combination of features describedabove, including the LCT core configuration, the relatively high percentof osmagent and, in some exemplary embodiments, the use of sorbitol asan excipient provides the desired ascending release rate over anextended time period from bi-layer oral osmotic dosage forms. Exemplaryembodiments of such bi-layer osmotic dosage forms are detailed below inExamples 1-3.

An embodiment of a bi-layer oral osmotic dosage form 15 is shown incross-section in FIG. 1. The components are not drawn to scale. Thebi-layer LCT core comprises a first component layer 21, containing drugand selected excipients, and a second push layer 29, containing at leastone fluid-expandable osmopolymer and optionally containing at least oneosmagent along with selected excipients. Suitable excipients are knownin the art and include diluents, carriers, binders, fillers andprocessing aids. A semipermeable membrane 57 surrounds the bi-layertablet core to form a compartment and a suitably sized orifice 55 isformed through the semipermeable membrane and into the first componentlayer 21 to permit drug formulation to be released from within thecompartment. As illustrated, the orifice 55 is preferably formed in thenarrow end of the dosage form comprising the first component layer. Inoperation, through cooperation of the bi-layer osmotic dosage formcomponents, drug is released from the first drug-containing layer at anascending release rate for an extended time period. Although not shownin FIG. 1, an immediate-release dose of a drug may be provided byapplying a drug-containing overcoat to a bi-layer dosage form, ifdesired, as described elsewhere herein.

In addition to the above-described bi-layer osmotic dosage forms, it hasbeen surprisingly discovered that oral osmotic dosage forms exhibitingan ascending drug release rate for an extended time period can also beachieved with a novel tri-layer tablet core surrounded by asemipermeable membrane and having suitable exit means for releasing drugformulation through the semipermeable membrane. The novel tri-layertablet core has a first drug-containing layer, a second drug-containinglayer and a third push layer. In operation, through the cooperation ofthe dosage form components, drug is successively released, in asustained and controlled manner, from the first drug-containing layerand then from the second drug-containing layer such that an ascendingrelease rate over an extended time period is achieved.

It has been discovered that a drug concentration gradient between thefirst and second drug-containing layers of the tri-layer corefacilitates the achievement of an ascending drug release rate for anextended time period from the tri-layer osmotic dosage form.Consequently, the other excipients in the drug-containing layers may bemore flexibly varied and adjusted for other purposes such asmanufacturing convenience and pharmaceutical elegance. For example, thetri-layer osmotic dosage forms preferably avoid the use of sorbitol asan excipient. This provides manufacturing efficiency and productshelf-life advantages since sorbitol is very hygroscopic and attractsmoisture during storage which can pose difficulties in handling andmanufacturing as well as longer-term stability concerns. In addition,sufficient activity in the push layer may be achieved with the use of arelatively lower concentration (less than about 25%) of osmoticallyeffective solute such that the size of the push layer can be smallerrelative to the size of the two drug-containing layers. Preferably, thepush layer is smaller than the combined size of the first and seconddrug-containing layers. An advantage to a smaller-sized push layer isthat larger doses of drug, if desired, can be accommodated without theoverall size of the dosage form becoming so large as to engendermanufacturing challenges and/or to become unpalatable to patients.

In a presently preferred embodiment, the hydration rate of the tri-layerosmotic dosage form is improved with the inclusion of a flux-enhancingagent in the semipermeable membrane. In addition, it is preferred to usethe longitudinally compressed tablet (“LCT”) core configuration, asdescribed above, for the tri-layer osmotic dosage forms to also enhancehydration. In a presently preferred embodiment, the combination offeatures including the LCT tri-layer core configuration, a suitable drugconcentration gradient between the first and second component layers,the osmotic properties of the component layers and the fluid fluxproperties of the semipermeable membrane achieves the desired ascendingrate of drug release over an extended time period. Advantageously, suchpreferred embodiments exhibit consistent and reliable operation and canbe efficiently manufactured on a large-scale basis.

A preferred embodiment of a tri-layer oral osmotic dosage formadditionally comprising an immediate-release dose of drug applied as anovercoat and an aesthetic overcoat 14 is shown in cross-section in FIG.2. The tri-layer LCT core comprises a first component layer 20,containing a selected drug in a pharmaceutically acceptable form alongwith selected excipients; a second component layer 18, containing ahigher concentration of drug along with selected excipients; and a thirdpush layer 28, containing at least one osmopolymer and optionallycontaining at least one osmagent along with selected excipients. Asemipermeable membrane 56 surrounds the tri-layer tablet core to form acompartment and a suitably sized orifice 54 is formed through thesemipermeable membrane and into the first component layer to permit drugformulation to be released from within the compartment. As illustrated,the orifice 54 is preferably formed in the narrow end of the dosage formcomprising the first component layer. In operation, through cooperationof the tri-layer osmotic dosage form components, drug is successivelyreleased, in a sustained and controlled manner, from the firstdrug-containing layer and then from the second drug-containing layer atan ascending release rate for an extended time period.

As shown in FIG. 2, the preferred embodiment further comprises animmediate-release dose of drug contained within an overcoat 60 appliedonto the surface of the tri-layer osmotic dosage form. The drug is mixedwith suitable excipients such as, for example,hydroxypropylmethylcellulose, to prepare a solution for coating onto thesurface of the semipermeable membrane of the tri-layer osmotic dosageform that will rapidly dissolve and release drug followingadministration.

As shown in FIG. 2, it is also preferred to provide an optionalaesthetic overcoat 62 applied onto the surface of the drug-containingovercoat 60. As known in the art, such aesthetic overcoats provideadvantages including taste-masking, improved appearance and“glidability” for facilitating swallowing and further processing stepssuch as printing, packaging, etc. Exemplary embodiments of tri-layerosmotic dosage forms that exhibit a substantially ascending release rateover an extended time period are detailed below in Examples 4-6 andExamples 8 and 9.

The continued maintenance of therapeutic effectiveness over a prolongedtherapy period by the administration of the oral osmotic dosage formsthat exhibit an ascending release rate over an extended time period ofthe present invention has been demonstrated. An exemplification isdescribed below in Example 7. In particular, it has been discovered thatsuch osmotic dosage forms containing methylphenidate can be used toprovide effective once-a-day therapy for ADHD. This discovery representsan important improvement in drug therapy for ADHD by eliminating theneed for multiple daily doses of methylphenidate yet providingtherapeutic efficacy throughout the day that compares to the therapeuticefficacy provided by multiple doses of immediate releasemethylphenidate.

The following examples are illustrative of the present invention, andthe examples should not be considered as limiting the scope of theinvention in any way, as these examples, and other equivalents thereof,will become apparent to those versed in the art in the light of thepresent disclosure and the accompanying claims.

EXAMPLE 1

Bi-layer oral osmotic dosage forms were made in accord with conventionalmanufacturing processes known in the art and disclosed in detail incopending U.S. application Ser. No. 967,606, filed Nov. 10, 1997, ofwhich the present application is a continuation-in-part application.Briefly, a first component layer, containing methylphenidatehydrochloride and selected excipients, and a second push layer,containing suitable osmopolymers, 40% by weight of an osmagent andselected excipients, were separately prepared by granulation methods.Next, the first component layer and the second push layer granulationpreparations were longitudinally compressed together to form bi-layerLCT cores. A selected semipermeable membrane was then coated around thebi-layer LCT cores and a suitable 30 mil orifice for drug release wasformed therethrough and into the first component layer.

Each dosage form as prepared comprised: First component layer 14.08 mgmethylphenidate hydrochloride 90.26 mg poly(ethylene)oxide (200,000number-average molecular weight)  5.5 mg poly(vinylpyrrolidone) (40,000number-average molecular weight)  0.11 mg magnesium stearate 0.555 mgbutylated hydroxy toluene Second push layer 71.032 mg poly(ethylene)oxide (7,000,000 number-average molecular weight)  52.8 mgsodium chloride  6.6 mg poly(vinylpyrrolidone) (40,000 number-averagemolecular weight)  1.32 mg red ferric oxide 0.132 mg magnesium stearate0.555 mg butylated hydroxy toluene Semipermeable Membrane  15.3 mgcellulose acetate (39.8% acetyl content)  1.7 mg poly(ethylene glycol)(3350 number-average molecular weight

The periodic release rates from the dosage form were determined hourlyfor ten hours using in vitro dissolution testing. A residual quantity ofdrug of 0.72 mg remained in the dosage form. The results are shown inTable 1 along with an indication of whether an ascending release rateoccurred. TABLE 1 Ascending Quantity of drug Release Rate Time (hours)released (mg) Occurrence 1 0.22 YES 2 1.45 YES 3 1.72 YES 4 1.84 YES 52.05 YES 6 2.21 YES 7 2.13 NO 8 1.26 NO 9 0.39 NO 10 0.09 NO

As seen from Table 1, drug was released from the dosage forms at anascending rate for an extended time period, i.e., more than 90% of thedrug was released by t=8 hours and ascending release rates occurredthrough t=6 an extended period of time well beyond the mid-point of theT₉₀.

EXAMPLE 2

Bi-layer oral osmotic dosage forms were made in accord with conventionalmanufacturing processes known in the art and disclosed in detail incopending U.S. application Ser. No. 967,606, filed Nov. 10, 1997, ofwhich the present application is a continuation-in-part application.Briefly, a first component layer, containing methylphenidatehydrochloride, sorbitol and selected excipients, and a second pushlayer, containing suitable osmopolymers, 40% by weight of an osmagentand selected excipients, were separately prepared by granulationmethods. Next, the first component layer and the second push layergranulation preparations were longitudinally compressed together to formbi-layer LCT cores. A selected semipermeable membrane was then coatedaround the bi-layer LCT cores and a suitable 30 mil orifice for drugrelease was formed therethrough.

Each dosage form as prepared comprised: First component layer (110 mg)12.8% methylphenidate hydrochloride 54.75%  poly(ethylene)oxide (200,000number-average molecular weight) 25.4% sorbitol   5%hydroxypropylmethylcellulose (11,200 number-average molecular weight)  2% magnesium stearate 0.05% butylated hydroxy toluene Second pushlayer (132 mg) 53.85%  poly(ethylene)oxide (7,000,000 number-averagemolecular weight)   40% sodium chloride   5%hydroxypropylmethylcellulose (11,200 number-average molecular weight)  1% red ferric oxide  0.1% magnesium stearate 0.05% butylated hydroxytoluene Semipermeable Membrane (42 mg) 47.5% cellulose acetate (39.8%acetyl content) 47.5% cellulose acetate (32% acetyl content)   5%poly(ethylene glycol) (3350 number-average molecular weight

The periodic release rates from the dosage form were determined hourlyfor twelve hours. No residual quantity of drug remained in the dosageform. T he results are shown in Table 2 along with an indication of theoccurrences of an ascending release rate. TABLE 2 Ascending Quantity ofdrug Release Rate Time (hours) released (mg) Occurrence 1 0.13 YES 21.16 YES 3 1.53 YES 4 1.61 YES 5 1.75 YES 6 1.79 YES 7 2.13 YES 8 2.18YES 9 1.07 NO 10 0.43 NO 11 0.17 NO 12 0.13 NO

As seen from Table 2, more than 90% of the drug was released by t=9hours and ascending release rates occurred through t=8 hours, anextended time period well beyond the mid-point of the T₉₀.

EXAMPLE 3

bi-layer oral osmotic dosage forms additionally comprising animmediated-released dose of drug applied as an overcoat onto thesemipermeable membrane were made in accord with conventionalmanufacturing processes known in the art and disclosed in detail incopending U.S. application Ser. No. 967,606, filed Nov. 10, 1997, ofwhich the present application is a continuation-in-part application.Briefly, a first component layer, containing methylphenidatehydrochloride, sorbitol and selected excipients, and a second pushlayer, containing suitable osmopolymers, 39.8% by weight of an osmagentand selected excipients, were separately prepared by granulationmethods. Next, the first component layer and the second push layergranulation preparations were longitudinally compressed together to formbi-layer LCT cores. A selected semipermeable membrane was then coatedaround the bi-layer LCT cores and a suitable 30 mil orifice for drugrelease was formed therethrough. A drug-containing overcoat mixture wasprepared and coated onto the semipermeable membrane of the osmoticdosage form. Optionally, a taste-masking overcoat is also applied.

Each osmotic bi-layer dosage form as prepared comprised: First componentlayer   14 mg methylphenidate hydrochloride   61 mg poly(ethylene)oxide(2,000,000 number-average molecular weight)  27.5 mg sorbitol  5.5 mgpolyvinylpyrrolidone  2.2 mg magnesium stearate 0.055 mg butylatedhydroxy toluene Second push layer   72 mg poly(ethylene oxide (7,000,000number-average molecular weight)   53 mg sodium chloride  6.6 mgpolyvinylpyrrolidone  1.3 mg red ferric oxide 0.132 mg magnesiumstearate 0.066 mg butylated hydroxy toluene Semipermeable Membrane   20mg cellulose acetate (39.8% acetyl content)   20 mg cellulose acetate(32% acetyl content)    2 mg poly(ethylene glycol) (4000 number-averagemolecular weight)

An immediate-release drug-containing overcoat comprising 60%hydroxypropylmethylcellulose and 40% methylphenidate hydrochloride isprepared and a final solution of 10 mg (i.e., containing 4 mg ofmethylphenidate salt) is coated onto the semipermeable membrane of theosmotic dosage form.

The periodic release rates from the drug overcoat and the osmotic dosageform were determined at 30 minutes, 1 hour and then hourly for the nextnine hours. The 4 mg of methylphenidate contained within the drugovercoat was released within the first 30 minutes and the periodicrelease rate shown at t=1 hour of 0.41 mg constitutes drug released fromthe bi-layer osmotic dosage form during the second 30-minute interval.No residual quantity of drug remained in the dosage form. The hourlyresults are shown in Table 3 along with an indication of the occurrencesof an ascending release rate. TABLE 3 Ascending Quantity of drug ReleaseRate Time (hours) released (mg) Occurrence 1 0.41 YES 2 1.05 YES 3 1.49YES 4 1.57 YES 5 1.71 YES 6 1.75 YES 7 2.09 YES 8 2.14 YES 9 1.32 NO 100.48 NO

As seen from Table 3, exclusive of the immediate-release drug overcoat,more than 90% of the drug was released by t=9 hours and ascendingrelease rates occurred through t=8 hours, an extended period of timewell beyond the mid-point of the T₉₀.

EXAMPLE 4

Tri-layer oral osmotic dosage forms were made in accord withconventional manufacturing processes known in the art and disclosed indetail in copending U.S. application Ser. No. 937,336, filed Aug. 19,1997, of which the present application is a continuation-in-partapplication. Briefly, a first component layer, containingpseudoephedrine hydrochloride and selected excipients, a secondcomponent layer, containing a higher concentration of pseudoephedrinehydrochloride and selected excipients, and a third push layer,containing suitable osmopolymers, an osmagent and selected excipients,were separately prepared by granulation methods. Next, the firstcomponent layer, second component layer and the third push layergranulation preparations were longitudinally compressed together to formtri-elected layer LCT cores. A selected semipermeable membrane was thencoated around the tri-layer LCT cores and a suitable 30 mil orifice fordrug release was formed therethrough.

Each dosage form as prepared comprised: First component layer 4.4 mgpseudoephedrine hydrochloride 15.3 mg  poly(ethylene)oxide (300,000number-average molecular weight) 1.1 mg hydroxypropylmethylcellulose(9,200 number-average molecular weight) 1.1 mg polyoxyethylene 40stearate 0.11 mg  magnesium stearate Second component layer 13.5 mg pseudoephedrine hydrochloride 2.59 mg  poly(ethylene)oxide (300,000number-average molecular weight) 0.9 mg hydroxypropylmethylcellulose(9,200 number-average molecular weight) 0.9 mg polyxyethylene 40stearate 0.018 mg  red ferric oxide 0.09 mg  magnesium stearate Thirdpush layer 22.2 mg  poly(ethylene)oxide (7,000,000 number-averagemolecular weight)  12 mg sodium chloride   2 mghydroxypropylmethylcellulose (9,200 number-average molecular weight)   2mg polyoxyethylene 40 stearate 1.2 mg cross-linked acrylic acid polymer0.4 mg red ferric oxide 0.2 mg magnesium stearate Semipermeable Membrane11.4 mg  cellulose acetate (39.8% acetyl content) 0.6 mg polyethyleneglycol (3350 average number molecular weight)

The periodic release rates from the osmotic dosage form were determinedhourly for 7 hours and results are shown in Table 4 along with anindication of the occurrences of an ascending release rate. TABLE 4Ascending Quantity of drug Release Rate Time (hours) released (mg)Occurrence 1 0.13 YES 2 0.65 YES 3 2.2 YES 4 2.78 YES 5 3.24 YES 6 3.14YES 7 3.43 YES

As seen from Table 4, about 87% of drug was released during the first 7hours and ascending release rates were achieved throughout this period.

EXAMPLE 5

Tri-layer oral osmotic dosage forms having a drug concentration gradientwherein the drug concentration was greater in the second component layerthan the first component layer and also having viscosity gradientswherein the viscosity of the first component layer was less than theviscosity of the second component layer and the viscosity of the secondcomponent layer was lower than the viscosity of the third push layerwere made in accord with conventional manufacturing processes known inthe art and disclosed in detail in copending U.S. application Ser. No.937,336, filed Aug. 19, 1997, of which the present application is acontinuation-in-part application.

Each dosage form as prepared comprised: First component layer (350 mg) 8.6% nicardipine 54.8% sorbitol 36.8% poly(ethylene)oxide (200,000number-average molecular weight) Second component layer (120 mg)   45%nicardipine   50% poly(ethylene)oxide (300,000 number-average molecularweight)   5% hydroxypropylmethylcellulose (9,200 number-averagemolecular weight) Third push layer (350 mg) 68.75%  poly(ethylene)oxide(7,000,000 number-average molecular weight)   20% sodium chloride   5%hydroxypropylmethylcellulose (9,200 number-average molecular weight)  5% cross-linked acrylic acid polymer   1% ferric oxide 0.25% magnesiumstearate Semipermeable Membrane (43.5 mg)   95% cellulose acetate (39.8%acetyl content)   5% polyethylene glycol (3350 average number molecularweight)

The dosage forms had 25 mil exit orifices formed through thesemipermeable membrane to permit release of drug formulation from withinthe compartment. An ascending release rate for an extended time periodof about 16 hours was achieved with the dosage forms of Example 5.

EXAMPLE 6

Preferred embodiments of the tri-layer osmotic dosage forms of thepresent invention additionally comprising an immediate-release dose ofdrug applied as an overcoat, as shown in FIG. 2, were prepared in accordwith conventional osmotic tablet manufacturing processes.

The first component layer contained the following (by weight percent):9.40% methylphenidate hydrochloride, 83.71% polyethylene oxide (PolyoxN-80 brand product of Union Carbide, Danbury, Conn.), 5%polyvinylpyrrolidone (Kolidon 29-32 product of BASF Corp., Mt. Olive,N.J.); 1.34% succinic acid; 0.5% stearic acid; and 0.05% butylatedhydroxy toluene.

The second component layer contained the following (by weight percent):13.65% methylphenidate hydrochloride, 78.80% polyethylene oxide (PolyoxN-80 brand product of Union Carbide, Danbury, Conn.), 5%polyvinylpyrrolidone (Kolidon 29-32 product of BASF Corp., Mt. Olive,NJ); 1.95% succinic acid; 0.5% stearic acid; 0.05% butylated hydroxytoluene; and 0.05% yellow ferric oxide, as coloring agent.

The third push layer contained the following (by weight percent): 73.7%high molecular weight polyethylene oxide (Polyox 303 brand product ofUnion Carbide, Danbury, Conn.), 20% sodium chloride; 5%polyvinylpyrrolidone (Kolidon 29-32 brand product of BASF Corp., Mt.Olive, N.J.); 0.25% stearic acid; 0.05% butylated hydroxy toluene; and 1% green ferric oxide, as coloring agent.

Each of the first component layer, second component layer and third pushlayer were separately prepared into granulated compositions in a fluidbed granulator. The granulated compositions were then compressedsequentially and longitudinally on a rotary tablet press to produce thetri-layer LCT cores. For each dosage form, 40 mg of the first componentlayer granulation and 75 mg of the second component layer granulationwere first sequentially filled and tamped at 100 newtons into the die.Then, 90 mg of the third push layer granulation to the die was added tothe die and the final compression was performed at 1500 newtons.

The composition of the semipermeable membrane was 83% by weightcellulose acetate (CA 398-10, having an acetyl content of 39.8%, productof Eastman Chemical, Kingsport, Tenn.) and 17% by weight copolymer ofethylene and propylene oxide (Poloxamer 188 brand product of BASF Corp.,Mt. Olive, N.J., added as a flux-enhancer. The two ingredients weredissolved in a blend of 99.5% acetone and 0.5% water to form a 5% solidssolution. In a pan coater, the solution was then sprayed onto thetri-layer LCT cores to a weight of 25.7 mg and a thickness of 4-5 mil.

After the semipermeable membrane had been applied to form a compartmentcontaining the tri-layer LCT cores, a 0.76 mm (40 mil) orifice wasdrilled through the semipermeable membrane at the narrow end of thecompartment proximate to the first component layer to thereby form thepreferred tri-layer osmotic dosage forms, each containing 14 mg ofmethylphenidate. Each dosage form was approximately 12 mm long with anapproximate diameter of 5.3 mm.

The drug overcoat for providing an immediate-release initial dose ofdrug contains approximately 30% by weight methylphenidate hydrochloride,approximately 70% by weight hydroxypropylmethylcellulose (Methocel E3brand name product of Dow Chemical Co., Midland, Mich.), and a traceamount of phosphoric acid (i.e., 20 ml of phosphoric acid added to 87 kgof drug in solution). An aqueous coating solution is prepared bydissolving and mixing the ingredients in water to form a solution with a10% solids composition. In a pan coater, the solution was then sprayedonto the semipermeable membranes of the tri-layer osmotic dosage formsto a weight of about 14.0 mg comprising an immediate-release dose ofmethylphenidate of about 4 mg.

The final aesthetic overcoat composition weighed 16.9 mg and containedan underlayer of Opadry II, yellow (brand name product of Colorcon, WestPoint, Pa. and an overlayer of Opadry, clear, with a trace amount ofcarnauba wax, a glidant, prepared and applied as follows: first, OpadryII (10%) is suspended in water (90%) and sprayed onto thedrug-overcoated dosage forms; next, clear Opadry (5%) is suspended inwater (95%) and sprayed onto the drug- and Opadry Il-overcoated dosageforms; finally, the dosage forms are tumbled in the coater with thecarnauba wax for ten minutes to allow about 100 ppm of wax to beuniformly distributed onto the clear Opadry overcoat.

Many pharmaceutical dosage forms utilize drug in salt form such as thehydrochloride salt of methylphenidate utilized herein. Such salt formsof drugs prepared in aqueous solution, however, are prone to degradationand, thus, often have stability and shelf-life problems. It has beendiscovered that the addition of an appropriate pH-adjusting agent to theaqueous solution decreases undesired degradation and improves thestability of the product. In particular, in preferred embodimentstri-layer osmotic dosage forms comprising methylphenidate hydrochloride,it has been discovered that degradation of the drug ingredient can beminimized by the addition of suitable antidegradation agents, i.e.,succinic acid in the first and second component layers and phosphoricacid in the drug overcoat. Other suitable antidegradation agents includecompounds that dissolve in an aqueous medium are pharmaceuticallyacceptable, i.e., nontoxic and suitable for oral administration tohumans, and that exhibit sufficient pH-adjusting ability, i.e., have apH no greater than 4 and preferably of 3 or below. Additional examplesinclude potassium phosphate, sodium phosphate, fumaric acid, citricacid, tartaric acid, malic acid, hydrochloric acid, aspartic acid,glutamic acid, oxalic acid, lactic acid, malonic acid, glyceric acid andascorbic acid.

Periodic release rates for twenty-four sample dosage forms prepare asdescribed were determined hourly for 12 hours and are presented in graphform in FIG. 3. The mean quantities released each hour are shown inTable 5. along with an indication of the occurrences of an ascendingrelease rate. It is noted that the entire 4 mg immediate-release dosewas essentialy released within the first hour and this quantity isdisregarded with respect to the determination that an ascending releaserate occurred at t=2 hours, i.e., the mean quantity at t=2 hours wascompared to the mean quantity at t=1 hours less 4 mg representing theimmediate-release dose TABLE 5 Ascending Quantity of drug Release RateTime (hours) released (mg) Occurrence 1 4.098 YES 2 1.138 YES 3 1.650YES 4 1.993 YES 5 2.043 YES 6 2.099 YES 7 1.966 NO 8 1.763 NO 9 0.428 NO10 0.174 NO 11 0.084 NO 12 0.061 NO

As seen from Table 5, exclusive of the immediate-release drug overcoat,more than 90% of the drug was released by t=8 hours and ascendingrelease rates occurred through t=6 hours, an extended period of timewell beyond the mid-point of the T₉₀.

EXAMPLE 7

Therapeutic effectiveness of single doses of tri-layer osmotic dosageforms containing 14 mg of methylphenidate and additionally comprising animmediate-release drug overcoat containing 4 mg of methylphenidate wasstudied and compared to multiple doses of immediate-releasemethylphenidate. Safety and therapeutic efficacy parameters wereevaluated for a 12-hour period in the same subjects treated with thefollowing regimens on different days: the experimental regimen whereinthe tri-layer osmotic dosage form was administered once at t=0 hours andthe standard regimen wherein immediate-release methylphenidate(Ritalin®) was administered three times, at t=0 hours, t=4 hours, andt=8 hours. Because the subjects were current methylphenidate users, thedoses of methylphenidate administered during each regimen variedsomewhat to match as closely as possible the “usual dose” each subjectwas routinely administered. For comparative purposes, the actual doseswere normalized to a single 18 mg dose of the tri-layer osmotic dosageand to 15 mg of Ritalin® administered as three 5 mg doses.

Plasma drug concentrations were determined in all subjects at the sametimes during the study periods for each regimen. The selected timescorresponded to the time just prior to, and 1.5 hours and 2.5 hoursfollowing, administration of the first two doses of immediate-releasemethylphenidate (i.e., at t=0 hours, t=1.5 hours, t=2.5 hours, t=4hours, t=5.5 hours, t=6.5 hours), and just prior to, and 1.5 hours and3.5 hours following, administration of the third dose (i.e., at t=8hours, t=9.5 hours and t=11.5 hours).

In FIG. 4, plasma drug concentrations obtained from one group of studyparticipants (n=16) while treated with the experimental regimen(represented by open diamonds) and while treated with the standardregimen (represented by closed circles) are shown in graph form. Acomparison of FIGS. 3 and 4 demonstrates a correlation between the invitro release rates through about t=8 hours and the in vivo plasma drugconcentrations through about t=9.5 hours.

As shown in FIG. 4, the plasma drug concentration following eachadministration of an immediate-release dose rises relatively rapidly andthen declines at a generally characteristic rate until the next dose isadministered. The plasma drug concentration following administration ofthe tri-layer osmotic dosage form also exhibits an initial relativelyrapid rise due largely to release of drug from the immediate-releasedrug overcoat. Subsequently, however, the plasma drug concentration doesnot decline but continues to substantially ascend (save for a slight“dip” between t=5.5 hours and t=6.5 hours) through a time period of 9.5hours. Particularly striking is the difference during the time periodswithin about 1 hour before and about 1.5 hours following administrationof the second and the third immediate-release dose. With the standardregimen, during these periods, the plasma drug concentration declines toa trough concentration and then rises again to a peak concentration.With the experimental regimen, during these same time periods, theplasma drug concentration is substantially smoothly ascending andexhibits no peaks and troughs.

Safety and therapeutic parameters, including behavioral, attentional andcognitive functions, were assessed hourly during the first three hoursand the last three hours of the study period and at two-hour intervalsin between. The clinical effectiveness of the experimental regimen wasclosely comparable to the clinical effectiveness of the standard regimenthroughout the twelve-hour study period. An effective once-a-day therapyfor ADHD provides many advantages and offers a significant improvementin drug therapy by eliminating the need for multiple daily doses ofmethylphenidate while providing continued therapeutic efficacythroughout the day.

EXAMPLE 8

Tri-layer oral osmotic dosage forms were made in accord with themanufacturing processes of Example 6 but comprising twice as muchmethylphenidate, i.e., a total of 28 mg of methylphenidate containedwithin the first and second component layers and 8 mg of methylphenidatein the drug overcoat. All of the remaining ingredients are also doubledso that the weight percents are the same as in Example 6. The third pushlayer is also doubled. The semipermeable membrane had the samecomposition as in Example 6 but was applied to a weight of about 34 mg.

These dosage forms exhibit release of 36 mg of methylphenidate withabout 8 mg released immediately and the remaining 28 mg released at anascending release rate over an extended time period.

EXAMPLE 9

Tri-layer oral osmotic dosage forms were made in accord with themanufacturing processes of Example 6 but comprising a total of 42 mg ofmethylphenidate contained within the first and second component layersand 12 mg of methylphenidate in the drug overcoat. The first componentlayer contained the following (by weight percent): 11.5% methylphenidatehydrochloride, 81.6% polyethylene oxide (Polyox N-80 brand product ofUnion Carbide, Danbury, Conn.), 5% polyvinylpyrrolidone (Kolidon 29-32product of BASF Corp., Mt. Olive, N.J.); 1.3% succinic acid; 0.5%stearic acid; 0.05% butylated hydroxy toluene; and 0.05% yellow ferricoxide, as coloring agent. The second component layer contained thefollowing (by weight percent): 19.8% methylphenidate hydrochloride,72.7% polyethylene oxide (Polyox N-80 brand product of Union Carbide,Danbury, Conn.), 5% polyvinylpyrrolidone (Kolidon 29-32 product of BASFCorp., Mt. Olive, N.J.); 1.95% succinic acid; 0.5% stearic acid; and0.05% butylated hydroxy toluene. The third push layer is doubled fromExample 6 and the semipermeable membrane had the same composition as inExample 6 but was applied to a weight of about 34 mg.

These dosage forms exhibit release of 54 mg of methylphenidate withabout 12 mg released immediately and the remaining 42 mg released at anascending release rate over an extended time period.

While there has been described and pointed out features and advantagesof the invention, as applied to present embodiments, those skilled inthe art will appreciate that various modifications, changes, additions,and omissions in the descriptions within the specification can be madewithout departing from the spirit of the invention.

1-34. canceled.
 35. A method comprising administering pharmaceuticallyacceptable composition comprising 100 ng to 500 mg of methylphenidateand a pharmaceutically acceptable carrier to said patient in a mannerthat achieves a substantially ascending methylphenidate plasma drugconcentration over a time period of about 5.5 hours following saidadministration.
 36. The method of claim 35 wherein said substantiallyascending methylphenidate plasma drug concentration is over a timeperiod of about 5.5 to about 8 hours.
 37. The method of claim 35 whereinsaid substantially ascending methylphenidate plasma drug concentrationis over a time period of about 5.5 to about 9.5 hours.
 38. A methodcomprises administering a pharmaceutically acceptable compositioncomprising 100 ng to 500 mg of methylphenidate and a pharmaceuticallyacceptable carrier to said patient in a manner that achieves asubstantially ascending methylphenidate plasma drug concentration over atime period of about 8 hours following said administration.
 39. A methodcomprising administering a pharmaceutically acceptable compositioncomprising 100 ng to 500 mg of methylphenidate and a pharmaceuticallyacceptable carrier to said patient in a manner that achieves asubstantially ascending methylphenidate plasma drug concentration over atime period of about 9.5 hours following said administration.